Understanding the Human Endocrine and Reproductive Systems

1. Unit 10 The Human Body Ch. 39 Endocrine & Reproductive Systems

2. The Endocrine System • The endocrine system is made up of glands that release their products into the bloodstream • These products deliver messages throughout the body

3. Hormones • Hormones - chemicals released in 1 part of the body, that travel through the bloodstream, & affect activities of cells in other parts of the body; “chemical messengers” • Target cells (receptor cells) - cells that have receptors for a particular hormone

4. Glands • A gland is an organ that produces & releases a substance, or secretion • Exocrine glands - release their secretions (hormones) through ducts (tubes), directly to the organs that use them

5. Glands • Endocrine glands - release their secretions (hormones) directly into the bloodstream

6. Major Endocrine Glands

7. Hormone Action • Steroid hormones: • Because they are lipids, they can cross cell membranes, passing directly into the cytoplasm & the nuclei of target cells

8. Hormone Action • Nonsteroid hormones: • They generally cannot pass through the cell membrane of their target cells

9. Prostaglandins • Prostaglandins - modified fatty acids that produce cells, affecting other nearby cells & tissues (“local hormones”) • Ex.) some cause smooth muscle tissue to contract

10. Control of the Endocrine System • Like most systems of the body, the endocrine system is regulated by feedback mechanisms that function to maintain homeostasis • Ex.) Pancreas releasing insulin: blood sugar level increases after lunch, pancreas releases insulin, blood sugar level decreases, pancreas stops releasing insulin

11. Human Endocrine Glands • The human endocrine system regulates a wide variety of activities • Any improper functioning of an endocrine gland may result in a disease or disorder

12. Human Endocrine Glands • The major glands of the endocrine system are: the pituitary gland, the hypothalamus, the thyroid gland, the parathyroid glands, the adrenal glands, the pancreas, & the reproductive glands

13. Pituitary Gland • Pituitary gland - divided into 2 parts: anterior & posterior; it secretes 9 hormones that directly regulate many body functions & controls the actions of several other endocrine glands

14. Pituitary Gland Hormones

15. Hypothalamus • The hypothalamus controls the secretions of the pituitary gland • The close connection between the hypothalamus & the pituitary gland, means that the nervous & endocrine systems can act together to help coordinate body activities

16. Thyroid Gland • The thyroid gland has the major role in regulating the body’s metabolism • Releases thyroxin which increases metabolism, & cellular respiration

17. Thyroid Gland • Unable to produce thyroxin produces condition known as cretinism • 2 effects of cretinism are dwarfism & severe mental retardation • Can be prevented by adding small amounts of iodine to table salt

18. Parathyroid Glands • The 4 parathyroid glands are found on the back surface of the thyroid gland • Hormones from the thyroid gland & the parathyroid glands act to maintain homeostasis of calcium levels in the blood

19. Adrenal Glands • There are 2 adrenal glands that sit on top of the kidneys, like little hats • The adrenal glands release hormones that help the body prepare for & deal with stress

20. Adrenal Glands • The 2 hormones secreted by the adrenal glands are: epinephrine and norepinephrine • The hormones produce the “fight or flight” response to stress

21. Pancreas • The pancreas has both exocrine & endocrine functions • It is a digestive gland whose enzymes help break down food • However, different cells in the pancreas release hormones into the blood

22. Pancreas • Insulin & glucagon are released from the pancreas to help keep the blood glucose level stable • Insulin stimulates liver cells to remove sugar from the blood & store it as glycogen • Glucagon stimulates the liver to break down stored glycogen & release sugar back into the blood

23. Pancreas • Diabetes mellitus - when the pancreas does not produce insulin • There are 2 types of diabetes, Type I and Type II • Type I requires daily injections of insulin, due to the fact that the body produces no insulin

24. Pancreas • Type II develops in people after the age of 40, produces normal insulin but cells don’t respond properly to the hormone • Usually controlled through diet, exercise, & medication taken orally

25. Reproductive Glands • The gonads are the body’s reproductive glands • They serve 2 important functions: the production of gametes & the secretion of sex hormones

26. Reproductive Glands • The female gonads are the ovaries - which produce eggs, & the hormones estrogen & progesterone • The male gonads are the testes - which produce sperm, & the hormone testosterone

27. The Reproductive System • Reproduction is the formation of new individuals • If any other system of the body failed, the result would be fatal, not the case with the reproductive system • Reproduction is important for continuation of the species, but not for that organism to survive

28. Sexual Development • For the 1st 6 weeks of development, male & female embryos are identical • During the 7th week, primary reproductive organs begin to develop • Hormones produced by those organs (gonads), will determine whether the embryo develops physically into a male or female

29. Sexual Development • Neither the testes nor the ovaries are capable of producing active reproductive cells until puberty • Puberty - a period of rapid growth & sexual maturation, when the reproductive system becomes fully functional

30. The Male Reproductive System • The main function of the male reproductive system is to produce & deliver sperm • Scrotum - external sac that holds the gonads, (external to reduce heat so sperm won’t die) • Seminiferous tubules - tiny tubules tightly coiled where the sperm are produced

31. The Male Reproductive System • Sperm - male sex cells (gametes)

32. The Male Reproductive System • Epididymis - structure that sperm move into, to mature & be stored until released • Vas deferens - tube that carries sperm from the epididymis, to the urethra, to be released • Penis - urethra carries sperm out of body through the penis

33. The Male Reproductive System

34. The Female Reproductive System • The main function of the female reproductive system is to produce ova (eggs) • In addition, the female reproductive system prepares the female’s body to nourish a developing embryo

35. The Female Reproductive System • Follicles - each ovary contains 400,000 clusters of cells surrounding a single egg, to help it mature • Ovulation - when a follicle has completely matured, its egg is released

36. The Female Reproductive System • Egg - female sex cells (gametes) • Fallopian tubes - tube from each ovary, that carries the egg to the uterus

37. The Female Reproductive System • Uterus - location of egg a couple days after ovulation, where embryo develops if fertilization takes place • Cervix - the outer end of the uterus • Vagina - a canal that leads to the outside of the body

38. The Female Reproductive System

39. The Menstrual Cycle • Menstrual cycle - when an egg develops & is released from an ovary • The menstrual cycle has 4 phases: follicular phase, ovulation, luteal phase, & menstruation

40. The Menstrual Cycle • The Follicular Phase • Development of an egg • Ovulation • Lasts 3-4 days, a mature egg is released into 1 of the fallopian tubes

41. The Menstrual Cycle • Luteal Phase • The remaining ruptured follicle, which continues to release hormones • Menstruation - when the lining of the uterus sheds, lasts about 3-7 days (period)

43. Sexually Transmitted Diseases • Sexually transmitted diseases - diseases spread from 1 person to another through sexual contact • Common STDs are chlamydia, syphilis, & gonorrhea (caused by a bacteria)

44. Sexually Transmitted Diseases • Others caused by viruses include: HIV, hepatitis B, genital herpes, & genital warts

45. Fertilization • When an egg is fertilized, the process of human development begins • In this process, a single cell, the size of a period at the end of a sentence, undergoes cell divisions that results in the formation of a new human being

46. Fertilization • Fertilization - the process of a sperm joining an egg, usually occurs in the fallopian tube • Zygote - a fertilized egg

47. Early Development • The stages of early development include: implantation, gastrulation, & neurulation • Implantation - when the blastocyst implants itself in the uterine wall • At this point, cells differentiate - develop into specific types of tissues in the body

48. Early Development • Gastrulation - the formation of 3 cell layers; the beginning of all of the organs & tissues of the embryo will form from these 3 layers

49. Early Development • Neurulation - the development of the nervous system, occurs shortly after gastrulation

50. Early Development • Placenta - connections between mother & developing embryo • The embryo needs a supply of nutrients & oxygen, & a way to get rid of carbon dioxide & wastes • Nutrients & oxygen diffuse from the mother’s blood into the baby’s blood